1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method for removing a periodic noise component included in an input image. The present invention also relates to a program for causing a computer to execute the image processing method.
2. Description of the Related Art
In order to reproduce a photographic image in ideal image quality, image processing such as gradation conversion processing, density correction processing, and sharpness processing has been carried out on an image. Especially, for an image obtained by reading a photograph with a scanner, periodic unevenness is observed therein due to performance of the scanner. In addition, moiré is observed in a part of an image obtained by reading an image including halftone dots. A periodic noise component such as periodic unevenness and moiré included in an image can be removed by carrying out frequency processing on the image.
For example, in U.S. Patent Application Publication No. 20010012407, a method has been proposed for removing a periodic noise component in a radiographic image caused by a grid used at the time of radiography. This method reconstructs the image by carrying out wavelet transform on the image for nullifying a signal component in a frequency band including a component representing the grid and by carrying out inverse wavelet transform thereafter.
However, if periodic noise components included in an image are in random frequency bands, judgment cannot be made as to whether the noise components are periodic unevenness or moiré or a frequency component representing a subject. For this reason, a frequency component representing a subject may be removed if the method described in U.S. Patent Application Publication No. 20010012407 is applied for removing a periodic noise component. Therefore, application of the method described in U.S. Patent Application Publication No. 20010012407 cannot remove a periodic noise component from an image with accuracy.